Fuel Pump Doesn't Prime in Ignition ON. Car starts fine.
09-12-12, 09:41 PM
#16
Okay, having your picture as a reference makes a little more sense. What voltage measurements would I see, if I had an FC signal during those first 3 seconds? I did not probe Pin #2, when I had someone turn the key. I probed Pin #3(output), thinking that if there was a signal, I would see 12.6V.
I think I'm misunderstanding how a relay works. On the control side, do I need to see 12.6v coming in and 0V(ground) going out? Should it look just like the EFI relay with the key ON?
EDIT: The more I think about what I've done and what you've said, the more it makes sense. In order for a relay to close, I need to have power on one side and ground on the other. That's why when I was testing for continuity, I had battery positive on one pin and battery negative on the second pin. So the computer grounds the relay for a few seconds, at least that's what it's meant to do. I haven't probed the relay with the engine running, I should do that to see how it's supposed to be.
If there is no ground signal with the Key On, does that mean my ECM is faulty? Can it be reprogrammed/reset?
Also, I now understand how a voltmeter works. My measurements in post #9 are worthless, because they were done incorrectly.
I think I'm misunderstanding how a relay works. On the control side, do I need to see 12.6v coming in and 0V(ground) going out? Should it look just like the EFI relay with the key ON?
EDIT: The more I think about what I've done and what you've said, the more it makes sense. In order for a relay to close, I need to have power on one side and ground on the other. That's why when I was testing for continuity, I had battery positive on one pin and battery negative on the second pin. So the computer grounds the relay for a few seconds, at least that's what it's meant to do. I haven't probed the relay with the engine running, I should do that to see how it's supposed to be.
If there is no ground signal with the Key On, does that mean my ECM is faulty? Can it be reprogrammed/reset?
Also, I now understand how a voltmeter works. My measurements in post #9 are worthless, because they were done incorrectly.
So if your relay are working and the fuel pump is not working, either you got an open circuit from the FC wire, or a faulty PCM/bad Transistor.
09-12-12, 10:38 PM
#17
On the power side of the relay, you should read source voltage. When the coil is energized, it becomes grounded, therefore, you should read 0V at the other end of the relay. So basically, 85 and 86 is the coil side of the relay, one of them is power(12V) and the other is ground(0V). 30 and 87(switch side) is the one that turns on the fuel pump. One side should be power(12V) and other is ground (0V).
So if your relay are working and the fuel pump is not working, either you got an open circuit from the FC wire, or a faulty PCM/bad Transistor.
So if your relay are working and the fuel pump is not working, either you got an open circuit from the FC wire, or a faulty PCM/bad Transistor.
09-13-12, 06:51 AM
#18
Do you know what controls the FC transistor, besides the crank sensor?
If you look at your schematic it shows a direct "BATT" wire to the ECM coming off the EFI relay. This is not a switch signal and is always supplied to the ECM. Another signal called "+B" is supplied to the ECM only with the EFI relay energized. I don't think the fuel pump would run without this signal present... so it is possible that it could be an internal ECM fault.
09-13-12, 09:16 AM
#19
Observe the valuable diagram he gave you. The STA and NE are the input signal to the PCM. FC is the output which is the transistor that grounds the the circuit opening relay to turn on the fuel pump. So if your inputs are doing their job but the output isnt, then you need to check if the transistor is actually providing ground.
09-13-12, 04:22 PM
#20
I confirmed that there is no Ground signal at Pin #2 of the CIRCUIT OPENING RELAY, upon turning the key to the ON position. As soon as I put the key in the ignition, the terminal gets up to 12.6V, then it just stays there when I go to the ON position.
When the engine is on, Pin #2 reads 80mV, while all the other three have battery voltage.
What would be my next logical step? And if it is an internal ECM failure, what are my options?
When the engine is on, Pin #2 reads 80mV, while all the other three have battery voltage.
What would be my next logical step? And if it is an internal ECM failure, what are my options?
09-13-12, 05:12 PM
#21
Then it looks like the ECM is not sending out the ground signal to turn on the relay. Another ECM would confirm this.
How bad is the fuel drop? If you were to fix your fuel pressure drop then that should help the longer cranking time.
The car takes a little longer than normal to start. Part of that problem is a fuel pressure drop, but that's for another thread.
09-13-12, 07:56 PM
#22
About the pressure drop, I believe it's on the fuel injector side. I have a bunch of new parts in the fuel tank (fuel pump, filters, fuel pressure regulator), so that side is good. Another reason I think it's the injectors is because I get a strong nasty odor on cold starts, as if there is too much fuel. Last time I measured, it drops to about 10psi over night.
09-14-12, 08:09 AM
#23
First about the ECM. How would I go about replacing the computer? Does it require reprogramming of all the keys, the security system, and the radio, etc.?
09-15-12, 10:46 AM
#24
I was thinking, what if my car was never intended to prime the fuel pump? What if I just assumed that all cars do this and that's what made me think that something is wrong?
Can somebody with a 3ES confirm that the fuel pump is activated when the key is turned to the ON position?
Can somebody with a 3ES confirm that the fuel pump is activated when the key is turned to the ON position?
09-17-12, 02:39 AM
#25
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Mr. Booby,
I understand the problem you are going through. I chased a similar problem down on a Toyota not long ago.
I had a no-start condition and was concerned that there was no power going to the fuel pump when the car key was cycled on. The only power I got to the Fuel Pump was when the engine was cranking. When attempting to turn over, the injectors were receiving power, as well as the plugs, so I felt that I had a fuel delivery issue. I checked all the fuel system relays, fuses and such but could not find any problems. I opened up the computer and found no burns, leaks or bad smells. I also was going to try to look at the ignition switch. Then I realized I was trying to solve this mystery the wrong way.
I was approaching this problem backward, because unlike other cars I have worked on, This Toyota did not have a Schrader valve that I could hook a fuel pressure gauge into, and I was not testing the fuel pressure (What I should have done in the first place).
So I made my own tool! I took a cut piece of hose that came off a donor vehicle with the clip that attaches to the engine (the kind you need the special release tool for) and I cut the end of a donor fuel rail which could be hooked into the fuel supply of the car. In between I had the pressure gauge. (I will try to post a pic)
What I noticed was that after 2 cranks, I had over 47 pounds of pressure (readings for this car were supposed to be between 42-50 PSI). So the problem I thought I had was not really a problem at all.
I diagnosed further and found I had a blown head gasket on cylinders 2 and 3.
The point is, you may want to check your fuel pressure first. Perhaps you have a weak fuel pump (probably not, since you said it is new). But perhaps you have a dirty or clogged injector.
Cheers!
I understand the problem you are going through. I chased a similar problem down on a Toyota not long ago.
I had a no-start condition and was concerned that there was no power going to the fuel pump when the car key was cycled on. The only power I got to the Fuel Pump was when the engine was cranking. When attempting to turn over, the injectors were receiving power, as well as the plugs, so I felt that I had a fuel delivery issue. I checked all the fuel system relays, fuses and such but could not find any problems. I opened up the computer and found no burns, leaks or bad smells. I also was going to try to look at the ignition switch. Then I realized I was trying to solve this mystery the wrong way.
I was approaching this problem backward, because unlike other cars I have worked on, This Toyota did not have a Schrader valve that I could hook a fuel pressure gauge into, and I was not testing the fuel pressure (What I should have done in the first place).
So I made my own tool! I took a cut piece of hose that came off a donor vehicle with the clip that attaches to the engine (the kind you need the special release tool for) and I cut the end of a donor fuel rail which could be hooked into the fuel supply of the car. In between I had the pressure gauge. (I will try to post a pic)
What I noticed was that after 2 cranks, I had over 47 pounds of pressure (readings for this car were supposed to be between 42-50 PSI). So the problem I thought I had was not really a problem at all.
I diagnosed further and found I had a blown head gasket on cylinders 2 and 3.
The point is, you may want to check your fuel pressure first. Perhaps you have a weak fuel pump (probably not, since you said it is new). But perhaps you have a dirty or clogged injector.
Cheers!
Last edited by KarlHungus; 09-17-12 at 06:03 AM.
09-17-12, 04:51 AM
#26
I was thinking, what if my car was never intended to prime the fuel pump? What if I just assumed that all cars do this and that's what made me think that something is wrong?
Can somebody with a 3ES confirm that the fuel pump is activated when the key is turned to the ON position?
Can somebody with a 3ES confirm that the fuel pump is activated when the key is turned to the ON position?
09-17-12, 05:08 AM
#27
Not all cars prime with key on engine off.
I called a few Lexus Dealers and asked if the fuel pump primes with key on and engine off and half says it does and half says it doesn't. Go figure!
I called a few Lexus Dealers and asked if the fuel pump primes with key on and engine off and half says it does and half says it doesn't. Go figure!
09-17-12, 08:47 AM
#28
Mr. Booby,
I understand the problem you are going through. I chased a similar problem down on a Toyota not long ago.
I had a no-start condition and was concerned that there was no power going to the fuel pump when the car key was cycled on. The only power I got to the Fuel Pump was when the engine was cranking. When attempting to turn over, the injectors were receiving power, as well as the plugs, so I felt that I had a fuel delivery issue. I checked all the fuel system relays, fuses and such but could not find any problems. I opened up the computer and found no burns, leaks or bad smells. I also was going to try to look at the ignition switch. Then I realized I was trying to solve this mystery the wrong way.
I was approaching this problem backward, because unlike other cars I have worked on, This Toyota did not have a Schrader valve that I could hook a fuel pressure gauge into, and I was not testing the fuel pressure (What I should have done in the first place).
So I made my own tool! I took a cut piece of hose that came off a donor vehicle with the clip that attaches to the engine (the kind you need the special release tool for) and I cut the end of a donor fuel rail which could be hooked into the fuel supply of the car. In between I had the pressure gauge. (I will try to post a pic)
What I noticed was that after 2 cranks, I had over 47 pounds of pressure (readings for this car were supposed to be between 42-50 PSI). So the problem I thought I had was not really a problem at all.
I diagnosed further and found I had a blown head gasket on cylinders 2 and 3.
The point is, you may want to check your fuel pressure first. Perhaps you have a weak fuel pump (probably not, since you said it is new). But perhaps you have a dirty or clogged injector.
Cheers!
I understand the problem you are going through. I chased a similar problem down on a Toyota not long ago.
I had a no-start condition and was concerned that there was no power going to the fuel pump when the car key was cycled on. The only power I got to the Fuel Pump was when the engine was cranking. When attempting to turn over, the injectors were receiving power, as well as the plugs, so I felt that I had a fuel delivery issue. I checked all the fuel system relays, fuses and such but could not find any problems. I opened up the computer and found no burns, leaks or bad smells. I also was going to try to look at the ignition switch. Then I realized I was trying to solve this mystery the wrong way.
I was approaching this problem backward, because unlike other cars I have worked on, This Toyota did not have a Schrader valve that I could hook a fuel pressure gauge into, and I was not testing the fuel pressure (What I should have done in the first place).
So I made my own tool! I took a cut piece of hose that came off a donor vehicle with the clip that attaches to the engine (the kind you need the special release tool for) and I cut the end of a donor fuel rail which could be hooked into the fuel supply of the car. In between I had the pressure gauge. (I will try to post a pic)
What I noticed was that after 2 cranks, I had over 47 pounds of pressure (readings for this car were supposed to be between 42-50 PSI). So the problem I thought I had was not really a problem at all.
I diagnosed further and found I had a blown head gasket on cylinders 2 and 3.
The point is, you may want to check your fuel pressure first. Perhaps you have a weak fuel pump (probably not, since you said it is new). But perhaps you have a dirty or clogged injector.
Cheers!
09-17-12, 10:20 AM
#29
You could do a fuel injector leak down test. If you could get your hands on a fuel injector pulse tester,
this would indicate which injector is leaking. You pressurize the system and connect the tester to each injector and it pulses the injector a predetermined amount of time. You need to have a fuel pressure gauge attached and measure the amount of drop for each injector. They all should read the same amount of drop.
this would indicate which injector is leaking. You pressurize the system and connect the tester to each injector and it pulses the injector a predetermined amount of time. You need to have a fuel pressure gauge attached and measure the amount of drop for each injector. They all should read the same amount of drop.
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